The invention relates to a chair, in particular an office chair. The chair has an inclinable backrest connected to a backrest carrier and the backrest carrier is supported on a seat carrier. A seat surface is provided which can be moved synchronously with the backrest. The seat surface is supported on the seat carrier via at least one seat link.
Seating furniture and, in particular, chairs in which the seat surface and the backrest move synchronously are used with various synchronizing mechanisms. The synchronizing mechanism serves to change the position of the seat surface at the same time as the backrest is adjusted.
A chair with synchronously adjustable inclination of the backrest and the seat is thus known from German Patent DE 37 35 256 C2. In the case of the chair, with a two-part seat surface, the rear edge of the seat surface is likewise lowered as the backrest is inclined. In its front region, the two-part seat surface is articulated on a non-pivotable seat carrier on each side by way of a pair of levers. In the rear region, the seat surface is connected rotatably on each side to a retaining part that is disposed rigidly on a rear carrier, the rear carrier being connected rigidly to the backrest. The seat surface is supported on the backrest carrier by way of its rear region. However, the two-part configuration of the seat surface, which is connected to a plurality of carriers of the chair by a total of two pairs of levers and two rotary articulations, involves a high outlay.
It is accordingly an object of the invention to provide a chair, in particular an office chair which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which has a particularly suitable synchronizing mechanism which can be realized in a straightforward manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a chair containing a seat carrier, a backrest carrier, a backrest supported on the backrest carrier and the backrest is able to be inclined in regards to the seat carrier, a seat surface, and at least one seat link connected to the seat carrier and to the seat surface. The seat surface is able to be moved synchronously with the backrest and is supported on the seat carrier through the at least one seat link. A coupling link for synchronization of a movement of the backrest and a movement of the seat surface is provided. The coupling link is connected rotatably, on a first side, to the seat surface and, on a second side, to the backrest carrier.
A coupling link is provided for synchronization between the movement of the seat surface and the movement of the backrest, the coupling link being connected rotatably, on one side, to the seat surface and, on the other side, to the link of the backrest.
The invention is based here on the consideration that, in the case of a chair or piece of seating furniture with an adjustable seat surface and adjustable backrest, the possible adjustments of the seat surface, on the one hand, and backrest, on the other hand, may first of all be regarded independently of one another. The configuration thus initially has two degrees of freedom. The possible adjustment of the backrest here has just a single degree of freedom if the backrest is articulated on the seat carrier in a straightforward manner via the backrest carrier, which is connected rigidly to the backrest and is fastened rotatably on the seat carrier via a single rotary spindle. Furthermore, the seat surface may have more complex possible adjustments, although, in a manner analogous to the adjustability of the backrest, it may be assumed that it is also possible to describe the possible adjustments of the seat surface with a single degree of freedom. The movement of the seat surface here may be both a translation and a tilting movement or a combination of different types of movement.
Coupling of the movements of the seat surface, on the one hand, and of the backrest, on the other hand, should first of all ensure here that each possible position of the backrest is assigned a position of the seat surface, as a result of which the entire configuration is limited to one degree of freedom. These requirements and a coupling mechanism which is of both permanently stable and straightforward configuration are fulfilled by a coupling link which is connected rotatably both to the seat surface and to the link of the backrest.
In an advantageous configuration, the seat surface is articulated on the seat carrier by two seat links or two respectively parallel pairs of links. In this case, the seat links are connected rotatably both to the seat carrier and to the seat surface. A seat link that is disposed in the front region of the seat surface, that is to say in the front half of the seat surface, which is directed away from the backrest, advantageously also serves here for length compensation in the case of an inclination of the backrest with the seat surface moved synchronously rearward and downward. An alternative configuration to this is a slot guide in the front region of the seat surface, in the case of which a spindle provided there on the underside of the seat surface is guided in an expediently horizontally running slot provided on the seat carrier.
In the configuration with the seat link, mounted rotatably on both end sides, in the front seat region for length compensation, the seat link is disposed in an inclined manner. In this case, the distance between a first, top point of rotation and the backrest, the front seat link being connected to the seat surface via the point of rotation, is smaller than the distance between a second point of rotation and the backrest. The first, front seat link being connected rotatably to the seat carrier via the second point of rotation.
In order to achieve mechanical loading and particularly suitable synchronization of the movements of the seat surface and of the backrest, a second seat link, which is provided in the rear seat region, i.e. in that half of the seat surface which is directed toward the backrest, is likewise disposed in an inclined manner.
For this purpose, the second seat link is connected rotatably, on the one hand, to the seat surface via a third point of rotation and, on the other hand, to the seat carrier via a fourth point of rotation. The distance between the third, top point of rotation and the backrest, in turn, is smaller than the distance between the bottom, fourth point of rotation and the backrest. It is expedient here for the angle of the rear, second seat link to the vertical to be greater than the angle of the front, first seat link to the vertical.
By virtue of the inclined configuration of the front, first seat link, which acts as length-compensation element, raising of the front edge of the seat surface as the backrest is inclined back is avoided in that, as the backrest is inclined back, the top point of rotation of the front seat link connected to the seat surface is lowered. The lowering action becomes more pronounced the more the inclination of the two seat links deviates from the vertical.
From the point of view of ergonomics, the comfort is increased by the comparatively pronounced inclination of the rear seat link in relation to the inclination of the front seat link in that, as the backrest is inclined back, the seat surface is lowered predominantly in its rear region. For this purpose, the rear, second seat link connected to the seat surface is at least 25% longer than the front, first seat link connected to the seat surface. As a result, the seat surface achieves, as desired, a greater freedom of movement in its rear region than in its front region.
In a particularly advantageous configuration, the point of rotation of the coupling link, provided for synchronization purposes, on the seat surface coincides with the point of rotation of the rear seat link, which connects the seat surface to the seat carrier. In order to achieve, in addition, both a particularly favorable kinematic functioning of the coupling mechanism and, at the same time, easy controllability of the mechanical loading states of the moving components, with the backrest not in an inclined position, the rear (second) seat link is expediently articulated on the seat surface, on the one hand, and on the seat carrier, on the other hand, such that it runs obliquely by an angle xcex2=(45xc2x130)xc2x0 in relation to the vertical. It is preferably the case that xcex2=(50xc2x110)xc2x0.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a chair, in particular an office chair, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.